Buggy code:
public class Parser { class SassTokenizer extends Tokenizer { public SassTokenizer ( Reader input ) { } @ Override protected Token fetchNumber ( ) { } @ Override protected boolean handleStringEscape ( char separator , char escapeChar , Token stringToken ) { } @ Override protected boolean isAtBracket ( boolean inSymbol ) { } @ Override protected boolean isAtStartOfIdentifier ( ) { } @ Override protected boolean isIdentifierChar ( Char current ) { } @ Override protected boolean isSymbolCharacter ( Char ch ) { } } private final Parser . SassTokenizer tokenizer ; private Stylesheet result ; public Parser ( String name , Reader input ) { } public Stylesheet parse ( ) throws ParseException { } private Section parseSection ( boolean mediaQuery ) { } private List < String > parseSelector ( ) { } private void parseVariableDeclaration ( ) { } private Expression parseExpression ( boolean accepLists ) { } private Expression joinOperations ( Expression result , String operation , Expression next ) { } private Expression parseAtom ( boolean acceptLists ) { if ( tokenizer . current ( ) . isNumber ( ) ) { return new Number ( tokenizer . consume ( ) . getContents ( ) ) ; } if ( tokenizer . current ( ) . isSpecialIdentifier ( "#" ) ) { return new Value ( tokenizer . consume ( ) . getSource ( ) ) ; } <START_BUG> if ( tokenizer . current ( ) . isIdentifier ( ) ) { <END_BUG> if ( tokenizer . next ( ) . isSymbol ( "(" ) ) { FunctionCall fun = new FunctionCall ( ) ; fun . setName ( tokenizer . consume ( ) . getContents ( ) ) ; tokenizer . consumeExpectedSymbol ( "(" ) ; while ( ( tokenizer . more ( ) ) && ( ! ( tokenizer . current ( ) . isSymbol ( ")" , ";" , "{" , "}" ) ) ) ) { fun . addParameter ( parseExpression ( false ) ) ; if ( tokenizer . current ( ) . isSymbol ( "," ) ) { tokenizer . consumeExpectedSymbol ( "," ) ; } else if ( ! ( tokenizer . current ( ) . isSymbol ( ")" ) ) ) { tokenizer . addError ( tokenizer . current ( ) , ( ( "Unexpected<seq2seq4repair_space>token:<seq2seq4repair_space>'" + ( tokenizer . consume ( ) . getSource ( ) ) ) + "'.<seq2seq4repair_space>Expected<seq2seq4repair_space>a<seq2seq4repair_space>comma<seq2seq4repair_space>between<seq2seq4repair_space>the<seq2seq4repair_space>parameters." ) ) ; } } tokenizer . consumeExpectedSymbol ( ")" ) ; return fun ; } else if ( ( tokenizer . next ( ) . isSymbol ( "," ) ) && acceptLists ) { StringBuilder sb = new StringBuilder ( tokenizer . consume ( ) . getSource ( ) ) ; while ( tokenizer . current ( ) . isSymbol ( "," ) ) { sb . append ( tokenizer . consume ( ) . getSource ( ) ) ; if ( ! ( tokenizer . current ( ) . isSymbol ( ";" , "(" , ")" , "{" , "}" ) ) ) { sb . append ( tokenizer . consume ( ) . getSource ( ) ) ; } } return new Value ( sb . toString ( ) ) ; } return new Value ( tokenizer . consume ( ) . getSource ( ) ) ; } if ( tokenizer . current ( ) . isSpecialIdentifier ( "$" ) ) { return new VariableReference ( tokenizer . consume ( ) . getContents ( ) ) ; } if ( tokenizer . current ( ) . isString ( ) ) { return new Value ( tokenizer . consume ( ) . getSource ( ) ) ; } if ( tokenizer . current ( ) . isSymbol ( "(" ) ) { tokenizer . consumeExpectedSymbol ( "(" ) ; Expression result = parseExpression ( true ) ; tokenizer . consumeExpectedSymbol ( ")" ) ; if ( result instanceof Operation ) { ( ( Operation ) ( result ) ) . protect ( ) ; } return result ; } if ( ( tokenizer . current ( ) . isSymbol ( "!" ) ) && ( tokenizer . next ( ) . isIdentifier ( ) ) ) { tokenizer . consumeExpectedSymbol ( "!" ) ; return new Value ( ( "!" + ( tokenizer . consume ( ) . getContents ( ) ) ) ) ; } tokenizer . addError ( tokenizer . current ( ) , ( ( "Unexpected<seq2seq4repair_space>token:<seq2seq4repair_space>'" + ( tokenizer . consume ( ) . getSource ( ) ) ) + "'.<seq2seq4repair_space>Expected<seq2seq4repair_space>an<seq2seq4repair_space>expression." ) ) ; return new Value ( "" ) ; } private Mixin parseMixin ( ) { } private void parseImport ( ) { } }

Fix:
if ( ( tokenizer . current ( ) . isIdentifier ( ) ) || ( tokenizer . current ( ) . isString ( ) ) ) {